Static compliance

Static compliance is usually higher than dynamic compliance because there is time for volume and pressure equilibration between the lungs and the measuring system. The measured volume tends to increase and the measured pressure tends to decrease, both of which act to increase compliance. Compliance is often plotted on a pressure-volume graph. 

The accuracy of press machines is limited mainly due to play in the drive system and compliance of drives and frame, giving rise to displacements of the slide under load in vertical and horizontal direction and by tilting. O-type frames suffer from horizontal displacements and tilting of the slide only with excentric loads from the process, while C-type frames have both also with centric loads. Even today measuring of dynamic behavior of press machines under dynamic loads is not standardized, but static compliances are standard quality parameters of press machines. 

Another important mechanical property of blood vessels in the compliance. Langewouters et al. [35] defined the static compliance as the derivative of equation (B6.3) with respect to pressure... 

Methodologies are currently available for measuring airway resistance and compliance in rodents and non-rodents either during spontaneous breathing (dynamic) or using a forced maneuver procedure (flow-volume or pressure-volume curves) that involves a controlled inflation and rapid deflation of the lung to evaluate forced expiratory flows and static or quasi-static compliance. The direct measurement of resistance and compliance t5q)ically requires an anesthetized model so that the airflows, pressures, and volumes can be monitored and controlled (Diamond and O DoimeU 1977 Costa et al. 1992 Mauderly 1989). 

As the lung is stretched, it acts as an expanded balloon that tends to push air out and return to its normal size. The static pressure-volume relationship is nonlinear, exhibiting decreased static compliance at the extremes of lung volume [Johnson, 1991 ]. As with tissue resistance, dynamic tissue compliance does not remain constant during breathing. Dynamic compliance tends to increase with increasing volume and decrease with increasing frequency [Stamenovic et al, 1990]. 

Jones AYM, Hutchinson RC, Oh TE. Effects of bagging and percussion on total static compliance of the respiratory system. Physiotherapy 1992 78 661-666. 

For some hood types, measurements usually seen as indirect method, are used to measure the hood s performance to determine regulatory compliance. For example, regulations specify minimum and maximum face velocities for laboratory fume hoods and static pressure (negative) inside enclosed hoods. Continuously monitoring instruments can be connected to alarms that sound when the measurement is outside the specified limits. 

Static lung compliance measurement, 3% Sulfates, 1 aerosols, 106-12 concentration, 112, 271-72 Sulfhydtyi compounds, effect of ozone on, 345-46... 

Mechanical testing was conducted on samples 25 mm in length, 10 mm in width and 0.1 mm in thickness, Because of the high compliance of the films, it was difficult to mount an extensometer on the samples to measure E. A DMA was therefore used to assess the elastic properties of the composite samples in the tensile mode of loading. A 5 N static tensile load and displacement amplitude of 16 /tm at a frequency of 1 Hz were applied. Nine measurements for each sample were made and the average values are reported here. 

Strictly speaking, there are no static viscoelastic properties as viscoelastic properties are always time-dependent. However, creep and stress relaxation experiments can be considered quasi-static experiments from which the creep compliance and the modulus can be obtained (4). Such tests are commonly applied in uniaxial conditions for simphcity. The usual time range of quasi-static transient measurements is limited to times not less than 10 s. The reasons for this is that in actual experiments it takes a short period of time to apply the force or the deformation to the sample, and a transitory dynamic response overlaps the idealized creep or relaxation experiment. There is no limitation on the maximum time, but usually it is restricted to a maximum of 10" s. In fact, this range of times is complementary, in the corresponding frequency scale, to that of dynamic experiments. Accordingly, to compare these two complementary techniques, procedures of interconversion of data (time frequency or its inverse) are needed. Some of these procedures are discussed in Chapters 6 and 9. 

In practice, viscoelastic properties can be determined by static and dynamic tests. The typical static test procedure is the creep test. Here, a constant shear stress is applied to the sample over a defined length of time and then removed. The shear strain is monitored as a function of time. The level of stress employed should be high enough to cause sample deformation, but should not result in the destruction of any internal structure present. A typical creep curve is illustrated in Fig. 13A together with the four-element mechanical model that can be used to explain the observations. The creep compliance represents the ratio between shear strain rate and constant stress at any time t. 

Total lung flow resistance Static lung compliance Flow resistance of airways... 

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